Apparatus for processing utility waste with bioderadable organic material content

ABSTRACT

An apparatus containing crushing screws ( 11 ) of the same pitch direction and without central shaft, provided with short drive shafts ( 112 ) on their driven end, wherein the rotational axis of the discharging screw ( 151 ) and the plane determined by the rotational axes of the two crushing screws ( 11 ) define an acute angle.

The invention relates to a method of processing utility waste of thetype of biomass, in particular sewage sludge, wastes of animal proteinprocessing, wastes of dairy industry, kitchen wastes, greasy sewage,etc. having organic material content.

The invention also relates to the arrangement of crushing and sortingunit and the heat treatment/mixing unit of the system for implementingthe method according to the invention.

Due to the increasingly stricter regulations of environment protection,the problem of treating and degrading/eliminating wastes containingorganic materials becomes more and more severe.

As a result of the sewage purification technologies, an extremely highamount of sewage sludge containing organic materials is produced in thesewage purification plants of the settlements.

The problem of treatment of sewage sludge can be regarded as solved. Inthe most common solution, the properly concentrated sewage sludge is fedinto a mezophilic and/or thermophilic fermentation tank, in which, afteran anaerobic treatment, biogas releases from the organic materialcomponent. This biogas is typically used for in-situ production ofelectricity.

For utilizing wastes containing organic materials, there have beenvarious methods used, many of which are—or were—under industrialproperty protection.

Such a method is disclosed in HU 204 481 (“Method for mezophilic orthermophilic, aerobic enzyme-based conditioning of liquid organicmaterials and biomasses”); HU 208 657 (“Apparatus for anaerobicpurification of sewage sludge”) or HU 200 139 (“Method for treatingliquids and sludges containing organic materials with environmentdamaging effects”).

These methods and apparatuses for carrying out the methods are notcapable or have only a limited capability of processing heterogeneousand dangerous materials.

A more complex solution is disclosed in HU 208659 (“Method for complexprocessing and utilization of municipal and agricultural wastes”).Although this method is theoretically suitable for treating materials ofvarious states of condition, however, it is not suitable for treatingwastes of foodstuff or foodstuff-like wastes that requirepasteurization. It has a further drawback that, depending on the type offeed, it requires the application of various additives, such as limecream, phosphor, potassium, etc. Yet another drawback is that thecontinuous operation cannot be guaranteed and it has not been disclosedwhat kind of apparatus can preferably be used to carry out the method.

An object of the present invention is to provide a method foreconomically and reliable processing various organic materials, alsoincluding biologically degradable materials that requirespasteurization, independently of their content and their state ofcondition, in a single, preferably closed-loop, continuously operatingsystem.

Another object of the invention is to provide apparatuses: crushing andsorting unit and heat treatment/mixing unit for the system carrying outthe method.

The invention is based on the idea that the very high amount of sewagesludge produced in the sewage sludge purification plants of thesettlements day by day and the high amount of household garbage andmunicipal waste produced in the same settlements, all containing organicmaterials can be treated together in a complex and economic manner.

We also recognised that the solid and/or liquid wastes containing solidmaterials, as well as biologically non-degradable mixed empties may becrushed and separated into a biologically degradable organic fractionand a biologically non-degradable fraction in one step, in a properlydesigned apparatus comprising crushing screws, stirring screws,discharging screws and briar teeth.

In addition, it was also recognised that in view of the economy in spaceand the energy consumption, it is preferred that the steps of heattreatment and mixing are carried out in one integrated unit.

The method of processing and utilizing wastes with organic, preferablyhigh organic material content, comprises by the steps of crushing thewaste in a crushing unit; heat treating, if needed and mixing thecrushed material with the sewage sludge; homogenizing the mixture;fermenting the homogenous material and directing the biogas obtainedinto a gas tank, which method is characterized according to theinvention by that the waste is crushed to pieces of 12 mm or smallersize, in a way that the empties are torn open and the organic residuestherein are discharged; the non degradable waste is separated and theorganic waste cleared from solid components is processed.

The waste and sewage sludge to be homogenised is preferably in the rangeof 1.2 to 0.8, more preferably 1.2 to 1.0 and advantageously 1:1 byvolume.

The solid material content of the sewage sludge homogenised ispreferably approximately 6%, at most 8%.

The temperature of the sewage sludge is held preferably in the range of35 to 55° C. during homogenization.

The crushing and sorting unit according to the invention comprisesreceiving tray, crushing screws and driving units, wherein the bottomplate of the receiving tray is perforated and formed as a screw housewith an open upper part for receiving a twin screw, two crushing screwsare arranged in said screw house; a chamber is formed under the bottomplate in order to accommodate one or more stirring screws; and adischarging assembly having a discharging screw is arranged at the endof the receiving tray opposite to the crushing screw driving unit, insuch a way that the free end of the discharging screw opposite to thedischarging screw driving unit intrudes into the operational space ofthe receiving tray), wherein the crushing screws are screws of the samepitch direction and without central shaft, provided with short driveshafts on their driven end, wherein the rotational axis of thedischarging screw and the plane determined by the rotational axes of thetwo crushing screws define an acute angle.

On the end plate of the receiving tray there are preferably a pluralityof briar teeth and a plurality of bits are preferably arranged on theend of the crushing screw.

The pitches of crushing screws may be made of multilayer metal sheets,are preferably identical with each other and adapted to rotateindependently of each other meanwhile their rotational speed may beadjustable. The non-driven end of the crushing screws is arranged closeto the end wall.

The discharging screw may turn back-and-forth and there may be one ormore separate discharge hoppers on the discharging assembly.

The heat treatment/mixing unit according to the invention comprises aheat treatment tank, a mixing tank and a mixer unit, wherein the heattreatment tank is arranged at the upper part of the mixing tankcoaxially surrounding the mixing tank; and the heat treatment tank andthe mixing tank are interconnected by a quick discharge assembly.

The heat treatment tank may be provided with internal and/or external,and the mixing tank with external heat insulation. The volume of theheat treatment tank is preferably less than the volume of the mixingtank.

The invention will now be described in more detail with reference to theaccompanying drawings.

FIG. 1 illustrates the technological flow diagram and the block diagramof the method and the system for implementing the method according tothe invention, respectively.

FIG. 2 shows a basic schematic line diagram of an exemplary embodimentof the crushing and sorting unit according to the invention, along amain sectional plane.

FIG. 3 is a schematic line diagram of the crushing and sorting unitshown in FIG. 2, along a transversal sectional plane.

FIG. 4 shows a schematic axonometric view of an exemplary embodiment ofthe crushing and sorting unit according to the invention, partly insection.

FIG. 5 is an enlarged detail (A) of FIG. 4

FIG. 6. shows a schematic axonometric view of the embodiment of thecrushing and sorting unit shown in FIG. 4. as viewed from anotherviewing point.

FIG. 7. illustrates a basic schematic line diagram of an exemplaryembodiment of the heat treatment/mixing unit according to the invention.

FIG. 8. shows an exemplary embodiment of the quick discharging assemblyof the heat treatment/mixing unit according to the invention,illustrated in closed position.

FIG. 9. shows an exemplary embodiment of the quick discharging assemblyof the heat treatment/mixing unit according to the invention,illustrated in open position.

For the sake of simplicity and better understanding of the description,the following references are used:

-   -   the solid wastes and/or the mixture of solid and liquid wastes        are referred to as mixed waste A, independently of their        content;    -   the liquid waste is referred to as liquid waste C, independently        of its content;    -   the sewage sludge produced in place is referred to as sewage        sludge D;    -   the delivered sewage sludge having a solid material content        equal to or less than 6% is referred to as sewage sludge D′;    -   the delivered sewage sludge having a solid material content more        than 6%, but less than 25% is referred to as sewage sludge D″.

As shown in FIG. 1 the mixed waste A and/or the sewage sludge D″ are fedinto the crushing and sorting unit 1. Alternatively, the liquid waste Cand/or the sewage sludge D′ may also be fed into the system at thispoint.

The unit is used for crushing the waste into chips of appropriatesize—up to 8 mm—, and for separating the biologically non-degradablematerials from the organic fraction.

Hereafter the biologically degradable organic fraction will be referredto as organic fraction B, whereas the biologically non-degradablefraction will be referred to as wastes H and H′.

Waste H contains mainly inorganic materials.

Waste H′ is a non-usable waste that contains a small amount of organicmaterial as well.

The organic fraction B of the mixed waste A is directed from thecrushing and sorting unit 1 into the mixing tank 32 or into the heattreatment tank 31 of the heat treatment/mixing unit 3 corresponding tothe position of the switching unit 2.

In case the waste, like the kitchen waste, requires pasteurisationbecause of its content, the waste is first directed into the heattreatment tank 31 and then into the mixing tank 32. When pasteurisationis not necessary, these wastes are directly fed into the mixing tank 32.

The biologically non-usable waste fractions H and H′ of the mixed wasteA are directed from the crushing and sorting unit 1 into wastecollection tanks 9 d and 9 d′, respectively, for further externalprocessing.

The liquid waste C and/or the sewage sludge D′ are directed also throughthe drawing-off station 5 into the mixing tank 32 or the heat treatmenttank 31 of the heat treatment/mixing unit 3 corresponding to theposition of the switching unit 2.

The appropriately pre-treated sewage sludge D and/or sewage sludge D′are fed into the mixing tank 32 of the heat treatment/mixing unit 3.

It is a matter of course that similarly to the organic fraction B andthe liquid waste C, the sewage sludge D and/or the sewage sludge D′ mayalso be fed through the switching unit 2 in the same way as mentionedbefore.

The heat treatment/mixing unit 3 has a double function:

-   -   heat treatment and pasteurisation of wastes that require        pasteurisation, such as wastes of animal protein processing,        kitchen waste;    -   mixing the organic fraction B and the liquid waste C with the        sewage sludge D and/or the sewage sludge D′ so that a sludge        composition with a consistence suitable for continuous        fermentation be produced. This sludge composition will be        referred to as sludge composition E.

The mixing ratio of the waste A and/or the liquid waste C to the totalsewage sludge D and/or the sewage sludge D′ is optimally 1 to 1 byvolume, but it may vary in the range of 1.2 to 0.8, preferably 1 to 1 byvolume.

The solid material content of the sludge composition E is optimallyequal to or less than 6%, but it may vary between 2% and 8%.

The sludge composition E is fed into the fermentation unit 4. It ispreferred that the fermentation unit 4 comprises both of a thermophilicunit 41 and a mezophilic unit 42.

The fermentation unit 4 is used to ferment the sludge composition Epreviously fed and to produce biogas from it.

The biogas G is directed from the fermentation unit 4 into the gas tank7 for further processing. The fermented sludge, also referred to asfermented sludge F, is convayed into the sludge treating block 9 a forfurther processing.

FIGS. 2 to 5 show an exemplary embodiment of the crushing and sortingunit according to the invention, which comprises a hopper 101 forreceiving the mixed waste A and/or the liquid waste C and/or the sewagesludge D″ and for storing them during the processing. The crushing andsorting unit 1 further comprises a perforated filtering bottom plate 102in the form of a screw house with an open upper part, a chamber 103arranged under said bottom plate 102, a suction stub 104 connected thechamber 103 for discharging the organic fraction B of the processedwaste, a receiving tray arranged on the end wall 105 and provided withbriar teeth 106, two crushing screws 11 arranged in the filtering bottomplate 102, one or more sliding screws 12 arranged in the chamber 103,driving units 13 for the crushing screws 11, one or more driving unit 14for each of the sliding screws 12, a discharging assembly 15 equippedwith a discharging screw 151 for discharging the biologicallynon-degradable fraction of the chipped waste, i.e. the wastes H and H′,said discharging assembly 15 being arranged at the end of the receivingtray 10 opposite to the driving units of the crushing screws andprovided with a discharging screw driving unit 152.

The discharging assembly 15 has one or more discharging hoppers, in caseof the above mentioned embodiment, two discharging hoppers 153, 154, fordischarging the wastes H and H′.

The crushing and sorting unit 1 is further provided with an industrialwater supplying pipe system 61 and a hot water supplying pipe system 62.

The most important feature of the receiving tray 10 is the perforatedfiltering bottom plate 102 formed as a screw house with an open upperpart, in which two crushing screws 11 are arranged in parallel. Thehopper 101 above the crushing screw 11 forms a high capacity storagevolume for receiving a large amount of waste at a time.

The filtering bottom plate 102 of the receiving tray 10 formed as screwhouse with an open upper part is perforated and adapted to properlyguide the two crushing screws separately while preventing them frombeing offset from their rotational axes. The curvature of the filteringbottom plate 102 is very similar to the curvature of the crest edge ofthe two crushing screws 11. The filtering bottom plate 102 is removableand in case of wearing, it may be replaced. The pattern of theperforation may be arbitrary, whereas the recommended maximum size ofthe perforations D is 10 or rather 8 mm, which allows solid materialsstill acceptable to pass therethrough into the fermenter. Anyway, inseveral cases the size of the perforations may be up to 12 mm. Beneaththe filtering bottom plate 102, there is a chamber 103 for receiving theliquid, biologically degradable material, i.e. the mixed waste A and/orthe liquid waste C and/or the organic fraction B of the sewage sludgeD″, all of them being fed into the receiving tray 10. Inside the chamber103, one or more sliding screws 12 rotate to prevent any deposition orblockage from being developed which would result in a malfunction. Thesuction stub 14 of the pump used to convey the organic fraction B forfurther processing is connected to the chamber 103, the outlet of saidsuction stub being scraped, cleaned and loosened by one of the slidingscrews 12 of the chamber in order to prevent any deposition from beingdeveloped on the suction stub 104.

The two crushing screws 11 of the crushing and sorting unit 1 is used tocarry out the substantial preparation and processing operations. Itsoperation is supported by its construction. The pitch and the rotationaldirection of the two crushing screws 11 are identical (both of thescrews are either right-handed or left-handed), thus their mutualseizure may be avoided even if the crushing screws 11 rotateindependently of each other. Due to the independent rotation of thecrushing screws, the material in the receiving tray 10 may be forced toflow in various directions while being stirred and chipped. Both of thecrushing screws 11 are formed without a central shaft, except adown-stream section of the driving unit, where they are provided with ashort stub shaft 112. The section without shaft is required to have highelasticity and flexibility, on the one hand, and high strength and hightorque transmission capability, on the other hand. Accordingly, it ismade of a multilayer plate resulting in high flexibility while havinghigh strength, heavy weight and high torque tolerating capability at thesame time. It has another very important feature: it has the greatestpossible diameter. The good preparation capability is due to all of itsdiameter, its flexibility, its weight and its torque toleratingcapability.

The big solid, occasionally frozen pieces of material are chopped anddisgregated by the two crushing screws 11 at a high efficiency. Thefiltering bottom plate 102 can clean and open up the blockedperforations easily due to its capability of easily fitting and easilyevading obstacles as a result of its flexibility, despite of its weight.It tears hardly any perforation and due to its flexibility, it evadesthe forces in spite of that there may be obstacles. A large diameter ofat least 700 mm allows solid materials (e.g. empties: cans, bottles,boxes and other containers) to enter in or exit from between the screwthreads. Due to the absence of shaft, the flow is also allowed insidethe closed space of the screw leaf adjacent to the rotational axis,therefore it performs a very definite and efficient crushing andrecovering operation of the bulk of the organic material.

The double crushing screw 11 has a further feature. At the end adjacentto its driving unit and to its short screw section with shaft, acutting-tearing-crumbling mechanism with a plurality of bits 111 isformed. According to the briar teeth 106 arranged on the end plate 105of the receiving tray 10, there is provided a stationary row of bits,whereas on the end of the rotational crushing screw 11, a moving row ofbits is arranged, as it is obvious from the above mentioned features.Thus the solid pieces in the material flow moving towards the wallhaving the stationary bits, including the beer cans as well, will be cutoff and made suitable for emptying.

The discharging assembly 15 equipped with a discharging screw 151 and adischarging screw driving unit 152 for discharging the biologicallynon-degradable fraction of the chipped waste, i.e. the waste H, isarranged at the end of the receiving tray 10 opposite to the drivingunit of the crushing screw 13. The axis of the discharging screw 151 andthe plane determined by the axes of the crushing screws 11 define anacute angle. The discharging assembly 15 starts to operate only when thecharged waste has been recovered, the major part of the organic fractionB has passed the perforation and substantially, only the leachedempties, solid pieces and other wastes H have been retained.

The two crushing screws 11 are driven by means of a frequency converter.It is preferred that an operator can control the rotational directionand the shut-down of the crushing screws 11 independently by using aradio frequency, portable switching device, thus it becomes possible fora properly skilled operator to mix materials that contain pieces withsize or condition which may be dangerous for the machine. The non-drivenend of the twin screw is close to the end wall, thus the waste can beefficiently discharged without leaving a dead zone.

In a preferred embodiment the hopper 101 of the receiving tray 10 can beopened mechanically, and can be closed for safety reasons, which allowsto reduce the effects of smell and noise. A suction cleaning system mayalso be connected thereto. For dilution and flushing, hot flush watermay be introduced into the inner space of the receiving tray 10.

In order to allow an even better flush, shower-like water injectionshould be provided. It is recommended to return some sludge from thefermenter. Optionally, the pump conveying from the apparatus to thefermenter is adapted for recirculation so that a larger portion of theorganic material can be washed.

In a preferred embodiment, the discharging assembly is ahigh-performance machine as the discharging assembly 15 may be filled upwith material being fed into the receiving tray 10 for separation. Thedischarging screw 151 of the discharging assembly 15 is than to berotated in reverse direction in order to return the mass with highorganic content to the receiving tray 10 for separation. In order tobetter compress the waste, the screws should be able lifting the wasteup to the half level, followed by returning and repressing it.

On the discharging assembly 15, two discharging hopper 153, 154 aremounted for depositing the wastes H and H′ in different directions bytype.

Under the discharging hoppers 153, 154, a compressing machine may bearranged that compresses the foreign packaging materials to be conveyedto the smallest possible volume. The bottom plate of the concrete objectlowered beneath the ground level for receiving the apparatus is inclinedand has an accumulating dibhole for collecting the escaped liquids.

For the installation of the crushing and sorting unit 1, it isrecommended that the apparatus should be accessible by lorries and heavytrucks and the road surface T in front of the apparatus should beavailable for transportation manipulations. The apparatus shouldprotrude from the plane of the road surface T at a minimum level in sucha way that the plane of the hopper extends at a distance of up to500-1000 mm from the road surface. The protrusion is provided to avoidan accident, however an excessive protrusion would make it impossiblefor the tip lorries to reverse and to discharge its load.

By using an adjustable protective screen, however, an adequateprevention of accidents may be reached.

FIG. 7 illustrates a basic schematic line diagram of an exemplaryembodiment of the heat treatment/mixing unit according to the invention,meanwhile FIGS. 8 and 9 show an exemplary embodiment of the quickdischarging assembly of the heat treatment/mixing unit according to theinvention, illustrated in the closed position and in the open position,respectively. Further to the structure of the heat treatment/mixing unit3, these figures also illustrate additional units and fittings thatpreferably enhance the operation of said unit or that are necessary touse.

One of the basic requirements for the proper operation of the anaerobicfermenters is to feed the material to be fermented (i.e. the sludge)into the fermenter uniformly and, if possible, continuously and in smalldoses rather than in bursts. The material to be fed should behomogeneous, and its temperature should have a value that does notdisturb the biological system operating in the fermenters. It is verydifficult to satisfy these condition in the case of lumpy organicmaterials originating from various locations, wherein said materials areto be treated in an anaerobic environment. If some portion of saidmaterials should be pasteurised (at 70° C.) as well, the problem to besolved would become even more complicated. Another significantdifficulty is that the anaerobic fermenters are extremely responsive tothe introduction of untreatable, lumpy materials. Such materialsaccumulate on the bottom of the fermenters and after a certain period,they block the pipes and the heat exchangers, which may finally resultin the shut-down of the fermenters.

The heat treatment/mixing unit 3 according to the invention is formed oftwo stacked, double-wall metallic tank. On the upper part of thecylindrical intermediate tank, i.e. the mixing tank 32, a shorter secondtank, i.e. the heat treatment tank 31, is fixed outside, wherein thevolume of the heat treatment tank 31 is less than that of the innermixing tank 32. The upper part is constituted by the heat treatment tank31 forming the pasteurisation zone, whereas the intermediate part isconstituted by the mixing tank 32 forming the mixing zone. In the mixingtank 32, the pasteurised materials are recooled, and mixed and dilutedwith the sewage sludge D produced by this technology. The mixing tank 32is also used to produce the homogeneous, uniform mixture for feeding itinto the fermentation units 4. Its internal volume is greater than itsexternal volume, which allows a quick discharge of the pasteurisationzone into the mixing zone. The mixing zone is equipped with a high-powermechanical mixer 33 that is adapted to recool the pasteurised materialsquickly.

The heat treatment tank 31 is preferably provided with a first heatinsulation 311 and an external heat insulation 312, whereas the mixingtank 32 is provided with an external heat insulation 312.

A powered quick discharging assembly 35, which can be opened and closedby power, is used to discharge the two zones quickly into each other bymeans of the gravitation. The discharging assembly of large diameterprevents any deposition from developing on the bottom of thepasteurisation zone. Due to its special design, the two zone canco-operate in the open state, thus the total capacity can be exploited.The mixing zone 38 is provided with a heat exchanger for the mixingzone, and the pasteurisation zone 37 is provided with a heat exchangerfor the pasteurisation zone. Due to the quick discharging assembly 35,the total capacity may be used for pasteurisation if needed.

In this embodiment, the switching unit 2 is in the form of a manifold 34extending inside the mixing tank and penetrating at the top of themixing tank 32, where it branches off to form two pipe sections, both ofthem being equipped with a powered slide gate, wherein one of thebranches is directed into the heat treatment tank 31, whereas the otherone is directed into the mixing tank 32. The bottom of the manifold 34is lead out downside, and the materials fed therein for treatment aredirected through the macerator 341 into either the pasteurisation zoneor the mixing zone easily and in a very simple way due to the manifold34. If necessary, the material to be treated can be recirculated throughthe macerator 341 during the pasteurisation as well in order to make thetreated material as fluent and uniform as possible with the lowestpossible heat loss, due to the application of the manifold.

The volume of the internal tank 32 of the heat treatment/mixing unit 3is greater than that of the external heat treatment tank 31, therefore acertain amount of cold sludge may be stored in the internal tank. Themixing tank 32 is equipped with a high-performance mechanical mixer 33adapted to quickly recool the pasteurised materials by mixing themrapidly with the cold sludge stored therein.

The method according to the invention will be described with referenceto a sewage purification plant as an example.

In the sewage purification plant, the materials are utilized ordestroyed by means of anaerobic fermentation. The types and thequantities of the used materials are listed below.

Rate of solid material Condition tons/day % Sewage sludge (producedliquid 54 in place) Sewage sludge (delivered) liquid 10 Wastes of animalprotein liquid 25 processing Wastes of dairy industry liquid/coarse 8Kitchen waste coarse 2 Greasy sewage liquid 1

The liquid wastes (wastes of animal protein processing, greasy wastes,liquid wastes of dairy industry), as well as the sewage sludge producedin other sewage purification plants (in pre-concentrated state) may bedelivered by tank vehicles of 6, 9 or 25 m³ capacity. The tank vehiclesdischarge the waste in a closed system, the waste being directed bymeans of pumps into a pasteurization zone of 65 m³ or a storage zone of54 m³ (for sewage sludge) of the pasteurization unit.

The kitchen wastes are delivered in closed barrels of 50 litres or inclosed containers with a volume of 9 m³ or 25 m³. Dairy products in cansor paperboards may be delivered on pallets. At the waste receivingstation 1 having a net capacity of 35 m3, both of barrels and tanks maybe deposited. The two crushing screws mounted in the drawing-off stationpresses the organic fraction of the waste through a perforated bottomplate made of carbon steel, said bottom plate having in this case agranular size of 12 mm. The waste may be diluted by either sewage sludgeor hot water. The crushed waste is conveyed to the pasteurization unitby means of stirring screws and pumps. The unrecoverable materials,empties etc. may be removed by means of discharging screws that performwater wash. The waste receiving station, the cover of which can beclosed, may be connected via an exhauster to a biofilter used foraerobic biological degradation of the smelly components.

At the receiving station, smell exhaustion must be provided. The netcapacity of the drawing-off station is 10 m³, while the appliedtechnology is the same as mentioned before.

The wastes directed through the crushing and grinding machines (i.e. thecoarse wastes) and the liquid wastes are directed into thepasteurisation unit comprising the two separate tanks. In thepasteurisation zone of said unit is used to carry out the optional heattreatment (at 75° C., the holding time is 1 hour). The wastes are heatedby means of a heat exchanger. The storage zone is used to mix the wasteswith each other and with the concentrated sewage sludge delivered to theplant or produced in place, as well as to make the mixture uniform forfeeding into the anaerobic fermentation technology. The mixing ratio ofthe waste and the sewage sludge is here approximately 1 to 1 by volume.

Subsequently, the mixed wastes are first fed into the thermophilicanaerobic fermenters (operating temperature: 55° C., net capacity: 2000m³), where the fermentation is completed at a high efficiency during a10 day holding time. The substantially fermented sludge discharged fromthe thermophilic unit and the major part of the concentrated sewagesludge produce in place are fed into the mezophilic anaerobic fermenters(operating temperature: 35° C., net capacity: 3×3000 m³), where theybecome fermented during a 14-16 day holding time. The assumeddegradation efficiency of the thermophilic-mezophilic system is 55-60%in respect of the organic material content, and the expected specificbiogas production (for 1 ton of degraded organic material) is in therange of 1100 to 1400 Nm³.

The gasification of the fermented sludge and the storage thereof beforedehydration are carried out in a post-fermenter (net capacity: 3000 m³)operating at variable operating levels without heating and mixing.

1-7. (canceled)
 8. A crushing and sorting apparatus preferably forprocessing wastes and sewage sludge with biodegradable organic materialcontent, comprising receiving tray, crushing screws and driving units,wherein the bottom plate (102) of the receiving tray (10) is perforatedand formed as a screw house with an open upper part for receiving a twinscrew, two crushing screws (11) are arranged in said screw house; achamber (103) is formed under the bottom plate (102) in order toaccommodate one or more stirring screws; and a discharging assembly (15)having a discharging screw (151) is arranged at the end of the receivingtray (10) opposite to the crushing screw driving unit, in such a waythat the free end of the discharging screw (151) opposite to thedischarging screw driving unit intrudes into the operational space ofthe receiving tray (10), characterized by that the crushing screws (11)are screws of the same pitch direction and without central shaft,provided with short drive shafts (112) on their driven end, wherein therotational axis of the discharging screw (151) and the plane determinedby the rotational axes of the two crushing screws (11) define an acuteangle.
 9. The crushing and sorting apparatus of claim 8, characterizedby that a plurality of briar teeth (106) are arranged on the end plate(105) of the receiving tray (10) and a plurality of bits (111) arearranged on the end of the crushing screw (11).
 10. The crushing andsorting apparatus of claim 9, characterized by that the pitches ofcrushing screws (11) are identical with each other.
 11. The crushing andsorting apparatus of claim 8, characterized by that the crushing screws(11) are made of multilayer metal sheets.
 12. The crushing and sortingapparatus of claim 8, characterized by that the non-driven end of thecrushing screws (11) is arranged close to the end wall.
 13. The crushingand sorting apparatus of claim 8, characterized by that the crushingscrews (11) are adapted to rotate independently of each other and theirrotational speed is adjustable.
 14. The crushing and sorting apparatusof claim 8, characterized by that the discharging screw (151) is adaptedfor turning back-and-forth.
 15. The crushing and sorting apparatus ofclaim 8, characterized by that there are one or more separate dischargehoppers (153, 154) on the discharging assembly (15). 16-19. (canceled)